1. Field of the Invention
The present invention relates to a technology for deleting data from a storage device.
2. Description of the Related Art
Image forming devices are often incorporated with a large-capacity storage device such as a hard disk drive (HDD). Such a storage device is used to temporarily store image data when, for example, a plurality of copies are produced from an image or duplex printing of an image is performed. The storage device is also used to store image data read by a scanner until the image data is downloaded to another electronic device via a network.
In recent years, with an increase in information crimes associated with networking as a background, there has been a growing trend to reinforce corporate information-security management, and authentication systems, such as Information Security Management System (ISMS), has started. In consideration of the risk of information leakage by extraction of a hard disk, in total corporate information-security management, data left in the large-capacity storage device incorporated in the image forming device poses problems that cannot be neglected.
To cope with such problems, Japanese Patent Application Laid-Open No. 9-223061 discloses a conventional technology in which a classified document mode can be set at a copier. When this mode is set, image data on a hard disk is deleted upon completion of the process of the image data.
Japanese Patent Application Laid-Open No. 2004-343157 discloses a conventional technology in which an area for overwrite-delete is checked to see whether to overwrite that area and, when it is determined to overwrite, overwrite-delete is performed.
However, in an overwrite-deletion process, resources, such as a central processing unit (CPU), are used for that process, and an access to storage medium is frequently repeated, which delays input/output processing speed.
To efficiently perform both overwriting process and input/output process, Japanese Patent Application Laid-Open No. 2004-288049 discloses a conventional technology in which a deletion process is started when a predetermined condition is satisfied. Japanese Patent Application Laid-Open No. 9-284572 discloses a conventional technology in which deletion process is started when the image forming device enters in idle state. With this, an overlap between an input/output process and a deletion process is avoided, thereby achieving efficiency in processing.
However, in the conventional technologies disclosed in Japanese Patent Application Laid-Open Nos. 2004-288049 and 9-284572, timing of overwrite-delete and a data input/output path are changed, and a process load in the overwrite process itself is still large for the efficiency in processing of the overwrite-delete. Moreover, the overwrite-delete still has a large influence on the input/output process of the image forming device. Furthermore, if security of the remaining data in a storage device is emphasized, sequential deletion is required in which the remaining data is immediately deleted when not required. With sequential deletion, there is a problem in which an overlap with the input/output process cannot be avoided.